By 1.9 million years
ago, some of the early transitional humans had
evolved into a new,
fully human species in Africa. Most paleoanthropologists refer to them as
Homo
erectus
(literally "upright human").
However, a few researchers split them into two species--Homo
ergaster(literally "working human") and
Homo erectus. The ergaster fossils were
presumably somewhat earlier
and have been found for the most part in Africa. The erectus discoveries have been found widespread in Africa, Asia,
and Europe. In this tutorial, ergaster and
erectus will be considered one species--Homo erectus.

Homo
erectus from Southeast Asia

Homo ergasterfrom
East Africa

Homo erectus were very
successful in creating cultural technologies that allowed them to adapt to
new environmentalopportunities.They were true pioneers in developing human culture
and in expanding their geographic rangebeyond Africa to populate tropical and subtropical zones elsewhere in the Old World.
This territorial expansion most likely began around 1.8-1.7 million years ago,
coinciding with progressively cooler global temperatures. Surprisingly, however,
Homo erectus remained
little changed anatomically until about
800,000 years ago. After that
time, there apparently were evolutionary developments in features of the head
that would become characteristic of modern humans. By half a million years ago,
some Homo
erectus were able to move into the
seasonally cold temperate zones of Asia and Europe. This migration was made
possible by greater intelligence and new cultural technologies,
probably including better hunting skills and the ability to create fire.

Evolutionary
Relationships

The
earliest Homo erectus were contemporaries of the late Homo
habilis in East Africa for several hundred thousand years.
This suggests that the immediate ancestor of Homo erectus was an early
Homo
habilis or possibly another yet to be discovered species of early humans.Homo erectus was a very successful human species, lasting at least
1.5 million years, though their numbers apparently remained relatively low.
Some of them eventually evolved into our species, Homo sapiens.
That evolutionary transition was well under way by
400,000 years ago but was not complete until
200,000-100,000 years ago and possibly even
later in some regions.

History
of Discovery

Eugene Dubois
(1858-1940)

In
the late 19th century, our knowledge of human fossil ancestors did not go back beyond that
of the Neandertals
in Europe, less than 100,000 years ago,
and little was known about them. There was no inkling of our
much earlier ancestors in Africa. A few scientists speculated that the most
ancient humans would be found somewhere in tropical
regions of East Asia. One of the people who held this
view was a Dutch anatomist and medical doctor named Eugene Dubois. Late in 1887, he
went to the Dutch East Indies (now Indonesia) as a military doctor. This
job allowed him enough spare time to pursue his passion, the search for
early human
fossils. He first explored the big island of Sumatra.
Excavating in several caves, he found a hominid jaw fragment in 1890. However, this
was not convincing evidence of early human ancestry. He then moved on to
Java. During excavations in the eastern part of that island in 1891-1892, he recovered a
Homo
erectus brain case and femur
(upper leg bone). Since he had discovered an unknown species, he took the liberty of naming it
in an 1894 publication. He called it Pithecanthropus erectus
(literally "ape man
who stands erect"). He returned to the
Netherlands with his fossils in 1895 and proclaimed
them to
be from our earliest ancestor. Unfortunately for Dubois,
most of the leading paleontologists of
his day were not convinced.

Dubois'
claims for his Java Homo erectus finds were not widely accepted until
the 1930's, when the German/Dutch paleontologist Gustav von Koenigswald made similar discoveries
in the Dutch East Indies. By
that time, there had also been even more convincing discoveries of Homo erectus in China.
Dubois, now in his 70's, stubbornly refused to accept any of these fossils as being from
the same species as his "Java Man" specimens.
He died at the outset of World War II, apparently as a rather lonely
maverick scientist frustrated by the inability to convince many people that
his conclusions had been correct.

Dating
the Java Homo erectus fossils has been difficult. In
the past, it was
generally accepted that most of these bones are 700,000-200,000
years old, based roughly on what
was the presumed date for the geological strata in which they were
found. In 1994, however, radiometric dating of sand particles attached
to two of the fossils indicated that they were actually 1.8 and 1.6 million
years old. These dates
indicate that some Homo
erectus left Africa soon after they evolved from early
transitional humans.

In
1911, a revolution in China overthrew the last emperor of
the Manchu Dynasty and set up a Western-style
republic under the leadership of the American-educated Dr. Sun Yat-Sen. In imitation of western
nations, the Geological Survey of China was established in 1917 with a Swedish
geologist named J. Gunnar Anderson as its advisor. Among the many tasks of the Survey was
the search for the
source of "dragon bones." This is a Chinese
generic term for the fossil bones that end up in apothecary shops as medicines. They are still popularly used
in a ground up form for healing wounds and fractures and treating cramps and
dizziness.
Some older
men in China use them as sexual stimulants, though they are being
replaced by modern drugs such as Cialis, Viagra, and Levitra.

Davidson Black
(1884-1934)

In
1921, Gunnar Anderson discovered that one of the important sources of
"dragon bones" in North China was an abandoned limestone quarry near
the village of Zhoukoudian.
This was only a day's drive over rough dirt roads from Beijing. In 1927, a fossil was found in
an ancient cave at the base of
the quarry that turned out to be a Homo erectus molar tooth.
It was examined by Davidson Black, a Canadian anatomy professor
at Peking Union Medical College. He identified the tooth as being from an earlier species of human
which he namedSinanthropus pekinensis
(literally "Chinese
man from Peking", or Beijing as
it is now called).This
discovery sparked 10 years of intense excavations at
Zhoukoudian by Anderson, Black, and others (especially
Pei Wenshong after 1929 and Franz Weidenreich in the mid-1930's). The bones of
50 individual
Homo erectus were eventually found there.

"Peking Man" skull

The Homo erectus skeletal evidence at
the "Peking Man" site of Zhoukoudian is especially important
because it is from a population of men, women, and children rather than just a
single individual. There was considerable sexual dimorphism and
individual variability. The human remains were associated with large
quantities of animal bones that apparently were mostly food refuse,
though many of them had been chewed by large carnivores and may have ended
up in the cave complex as a result of their activities. A
few of the bones had been burned in a way that suggests cooking. In addition, more
than 100,000 stone, bone, antler, and horn tools were excavated. The
cave was intermittently occupied by late Homo erectus for
around 300,000 years, beginning around780,000 years ago.

With
the exception of two teeth, all of the Homo erectus bones from
Zhoukoudian were lost in the chaos of late 1941 when the Japanese Army invaded Beijing
and other urban centers in eastern China. There have been a number of intriguing guesses about what happened to the bones.
The last time they were
accounted for was when they were turned over to a U.S. Marine detachment,
placed in wooden foot-lockers, and possibly taken 140 miles from Beijing to
the American Camp
Holcomb. They were to be transportedby ship to the U.S. for safety on
an American freighter named the President Harrison. However, after the U.S. entered the war on
December 7, 1941, Japanese forces quickly seized Camp Holcomb. At that
point in time, the Zhoukoudian fossils disappeared and have never reappeared. In 1949, the Peoples Republic of China established a $100,000
reward for their return. Unfortunately, it has not been claimed.
The only surviving bones were the two teeth that had not been turned over to the
Marines in 1941.

The
loss to science of the Zhoukoudian bones was not as great as it may initially
seem. Earlier, they had been measured, photographed, and excellent casts of them had been successfully sent to the
U.S. by Franz Weidenreich where they were kept safe during
World War II. In addition, other Homo erectus skeletal material has been
excavated in China since the mid 1960's. Most notably are the finds that
were recovered from Lantian County, Shensi Province. These
fossils from several Chinese sites date to at least 800,000 years ago.

"Turkana Boy"

In 1960, Louis and Mary Leakey found a 1.25 million year old
Homo
erectus partial cranium at Olduvai Gorge. Subsequently, more
Homo erectus fossils
were discovered there and at other sites in East, South, and Northwest Africa.
The oldest known Homo erectus date to nearly 2 million years ago in
East Africa. This strongly suggests that Homo erectus originated there. In 1984,
Richard Leakey's team
working at Nariokotome on the western side of
Lake Turkana found a nearly complete Homo erectus skeleton of an
8-12 year
old boy dating to 1.6 million years ago. It is
usually referred to as the
"Turkana Boy." The
significance of this discovery will be discussed below.

Three surprisingly early Homo erectus skulls were found
during the 1990's on
the fringes of Eastern Europe at Dmanisi in the Republic of Georgia. They
date to 1.75 million
years ago and look very much like the earliest Homo
erectus from Africa--i.e., those that have been classified by some
researchers as Homo ergaster. This
discovery lends credence to the 1.8 and 1.6 million year old dates for Homo
erectus from Java and to an early rather than late Homo erectus
expansion out of Africa.

Homo erectus-like bones were
also discovered during the 1990's from several other
sites in Western Europe and Africa that date 800,000-400,000 years ago.
It has been difficult to assign these fossils to specific species due to the
fact that they have characteristics of both Homo erectus and
more recent human species.
Some paleoanthropologists consider them to be late
transitional Homo erectus. Others now
suggest that they are Homo heidelbergensis,
a subsequent species
that descended from Homo erectus and preceded
Neandertals and other archaic humans. That
is the approach taken in this tutorial series.This
particular difference of species assignment is not particularly important and it does not
detract from our growing understanding of the broad evolutionary trends. It is
a result of our evolving conceptualization of the past as more data become
available. It also partly reflects the fact that the picture of human
evolution looks somewhat dissimilar in different regions of the World. It is now becoming clear that our evolution
was not as straight forward as it once was commonly thought.
Humans in some areas lagged behind. This was particularly true on some
islands of Indonesia. At Ngandong
on Java, for instance, Homo erectus may have survived to 53,000 years
ago or even somewhat later.

Important Homo erectus
Sites

Date of Fossil
(years ago)

Cranial Capacity(in cm.3)

Africa:

East
Turkana

1,900,000-1,600,000

850-900

West
Turkana

1,500,000

OlduvaiGorge

1,300,000-700,000

1067

Bouri

1,000,000

Swartkrans

1,800,000-1,500,000

Ternifine

700,000-500,000

Sale

400,000

900

Israel:

Ubeidiya

1,600,000-1,400,000

Europe:

Dmanisi

1,750,000

600-650

Atapuerca

1,200,000

-

Java:

Modjokerto

1,800,000

----

Sangiran

1,800,000-1,600,000

813-1059

Trinil

900,000
?

----

Ngandong

546,000-143,000 ?

China:

Yuanmou

1,700,000 ?

Lantian

800,000

780

Zhoukoudian

770,000-400,000

850-1250

Hexian

400,000

1025

Note: Several human fossils dating 800,000-400,000 years ago are controversial. They are
classified as Homo erectus by some researchers and Homo
heidelbergensis (a later human species) by others. They will
be presented in the next tutorial of this series.Note: It is likely that Homo erectus
reached Java and other Indonesian islands during glacial periods when
sea levels were low enough to create a land connection with the
Southeast Asian mainland.

Homo erectus
Anatomy

Homo
erectus

Below the neck, Homo erectus
were anatomically much like modern humans. Their arm
and leg bones were essentially the same as
modern people in shape and relative proportions. This strongly supports
the view that they were equal to us in their ability to walk and run bipedally. However, their leg bones were apparently denser than ours.
This may be partly a result of developmental adjustment differences.
Unlike us, these early humans did not spend much of their lives sitting
behind desks or on a sofa watching TV. They
were probably much more active throughout the
day seeking food.

Their legs would have made Homo
erectus efficient long distance runners like modern humans. It has
been suggested that this capability would have allowed them to run down
small and even medium size game animals on the tropical savannas of
East Africa. If this was the case, it is also
likely that they were largely hairless by this time. Bodies with
little hair are more efficient at remaining cool via the evaporation of
sweat during times of heavy exertion. Four legged mammals primarily cool their bodies by panting. Because
they are unable to pant while galloping, they readily overheat in hot
weather. As a consequence, they cannot run long distances without
collapsing from heat exhaustion. This gives human hunters a
decisive advantage when chasing them.

It also has been suggested that the pelvis in
early Homo erectus may have been a bit narrower than in modern
humans, which would require the infant brain to be smaller at birth and to
then undergo considerable growth in childhood. However, we must be
careful to not make too much of these differences because the number of
existing specimens is low and there were minor regional variations as well.
This becomes apparent especially when comparing Homo erectus from
East
Asia and Africa.

With
the evolution of Homo erectus, there was a significant increase
in body size compared to earlier hominids. Past estimates of Homo erectus stature frequently were in the 5-5½
feet (152-168 cm) range for adult males and around
88-150 pounds
(40-68 kg). The discovery of the "Turkana Boy" in
1984 brought this into question. This is not only the most complete specimen
of this species so
far discovered,
but it is one of the earliest.
The boy was only 8-12 years old when he
died but already 5 feet 3 inches (160 cm) tall. If he had lived to adulthood, he
very likely would have grown to 6 feet (180 cm), assuming
that Homo erectus growth patterns were similar to ours. As the number of nearly
complete Homo erectus skeletons increases in the future, a clearer
understanding of the range of their stature and body shape will likely emerge.

Homo erectus
heads were
strikingly different from ours in shape. They had
relatively strong muscles on the back of their necks. Their foreheads were shallow, sloping
back from very prominent bony brow ridges (i.e., supraorbital tori).
Compared to modern humans, the Homo erectus brain case was more
elongated from front to back and less spherical. As a
consequence, the frontal and
temporal lobes of their brains were
narrower, suggesting that they would have had somewhat lower mental ability.

Homo erectus (from Java)

Homo sapiens
(modern human)

shovel-shaped
incisors

The adult
Homo erectus brain size ranged from around 750 to1250 cm3,
averagingabout 930 cm3.
This was only around 69% the size of modern human brains on average but 50%
larger than Homo habilis. The upper end of the Homo erectus brain size range overlapped
that of modern people. However,
the larger brained Homo erectusmostly were relatively late in time and are considered by some
paleoanthropologists to be a more recent human
species (Homo heidelbergensis or early archaic
humans).

Homo
erectus teeth were generally intermediate between modern humans and the
australopithecines in shape and size. The teeth of later Homo erectus
were generally smaller than the earlier members of this species.
This was particularly true of molars. This evolutionary
trend probably reflects a progressive change in diet to softer foods,
including more meat and eventually cooked food. The incisor teeth of
Homo erectus generally have a "scooped out" appearance on the tongue
side. These "shovel-shaped" incisors are also found among many
Asians and Native Americans today.

It is likely that increased meat
consumption had a significant impact on the biological success of early
humans. It provided the calories in a more easily digestible,
concentrated form needed to maintain larger brains. The additional
useable calories also made it possible for women to have shorter time
periods between pregnancies and to subsequently give birth to more children
during their reproductive years. As a result, there was an
acceleration of human population growth which was very likely an important
contributing factor in the spread of people out of Africa and into Asia and
Europe for the first time.

Food
For Thought: Meat-Based Diet Made Us Smarter--audio
recording of an NPR interview with
anthropologists
Leslie Aiello and Richard Wrangham concerning
the relationship between switching
from a predominantly vegetable diet to one
that contains large amounts of meat and the evolution of
large human brains. This linktakes you to an external website. Toreturn here, you must click the"back"
buttonon your browser program.(length = 7 mins,
46 secs)

Homo
floresiensis

In 2003, a team of
Australian paleoanthropologists led by Peter Brown discovered
a skeleton from what may be a dwarf Homo erectus or
related species that lived until 18,000 years ago on Flores Island, Indonesia.
This 30 year old adult female was only about 3 feet 6 inches tall (106
cm), 66 pounds (30 kg), and had a brain
size of 380 cm3 (like
those of australopithecines, barely 1/3 as big as modern human brains). This find
implies that a population of exceptionally small Homo erectus or Homo erectus-derived
humans survived on this relatively isolated island east of Java until far
later than previously believed. Brown refers to this new
discovery as Homo floresiensis.
The bones of 8 additional individuals of this cave dwelling population were
subsequently found on Flores Island.

At present, there is no clear consensus
among paleoanthropologists as to the place of floresiensis in human
evolution.Peter Brown and his colleague, Michael
Norwood, suggest that floresiensis may have been a descendent of
normal size Homo erectus who arrived in this area of Indonesia about
800,000 years ago or even earlier and that they became small as a result of a well known
biological phenomenon referred to as "island dwarfing". They also
believe that floresiensis may have survived on the island until a
devastating volcano wiped them out, along with dwarf elephants, around
12,000 years ago. Critics suggest that the Flores Island dwarfs were,
in fact, modern people who suffered from microcephaly, a pituitary gland
disorder known as Laron syndrome, or hypothyroidism due to a lack of iodine
in their diet.

The short video clip and the narrated slide
show linked below will help you get a better
understanding of this intriguing discovery.

Hobbits on Flores, Indonesia--A tiny
hominin found on the island of Flores, Indonesiahas shaken up the world of paleoanthropology. Human
Origins scientist Matt Tocheri explains why.This link takes you to an external
website. To return here, you must click the "back"buttononyour browser program.
(length = 4 mins
19 secs)

Just how
long humans have been on Flores Island is not clear.
The volcanic ash layer above several simple flake artifacts found there has
been dated with the argon/argon radiometric method to 1.08-1.02 million
years ago. Presumably, this sets a minimum age for Homofloresiensisor their predecessors on
the island.

NEWS:In
the August 9, 2007 issue of Nature, Fred Spoor et.al., reported that
a 1.44 million year old Homo habilis fossil was found at the Koobi Fora
Formation east of Lake Turkana in Kenya. If this date proves to be
reliable, it will confirm that Homo habilis lived until several hundred
thousand years later than previously assumed. It also provides
additional support for the assumption that Homo habilis was a contemporary
of early Homo erectus rather than only a predecessor.

NEWS:In
the February 27, 2009 issue of Science, Matthew Bennett et.al.,
reported the discovery of 2 sets of 1.51-1.53 million year old Homo erectus
footprints near Lleret, Kenya. These prints are said to be essentially
like those of modern humans.

NEWS:In
the March 11, 2009 issue of Nature, Guanjun Shen et.al., reported
that a joint Chinese and American research team was able to date the lower
occupation levels at Zhoukoudian to 680,000-780,000 years ago using a new
radiometric method based on the decay of aluminum and beryllium isotopes (26Al
and 10Be) found in quartz grains.
These dates place Homo erectus at Zhoukoudian around 200,000 years earlier
than previously thought. It also establishes that they were present at
the time of a mild glacial period.

NEWS:In
the May 7, 2009 issue of Nature, W. L. Jungers et.al., reported
that the feet of Homo floresiensis were relatively long with stubby big toes
and no arches. This means that their feet had a combination of
human and early hominin traits and implies that their gait was not as
efficient as that of modern humans for long distance walking.